instrument voltage limiter conversion question... its getting really HOT!!!!

[resq302]

Ok, I went ahead last year and did the electronic conversion for the instrument voltage limiter for my 69 charger that I saw on Moparts.  Here is the link -  http://www.moparts.org/Tech/Archive/elec/11.html  .   I noticed that when I was doing some other work under the dash, that the metal casing on the voltage limiter was extremely hot to the point I would burn my hand or finger if I touched it. I used one of the laser infrared thermometers and with the car idling for about 5-10 mins, the casing of the voltage limiter got up to temps of 210 ferenheight. To me that is WAY too hot. Is that what they are normally supposed to be at or are they supposed to be a lot cooler? I know the conversion on my parents 70 chally vert that does not have the rallye dash does not get hot like this but it only has the temp and fuel gauge vs. the temp, fuel, and oil pres. gauge that my charger has.

Can anyone shed some light on this before my charger goes up in flames?

Thanks,

Brian

[Topher]

Never tested the temp on mine, but it will burn me if I grab it. Did you solder it to the case? If so, the case acts like the heat sink to remove the heat from the chip so it lasts longer.

[69DodgeCharger]

Ok, I went ahead last year and did the electronic conversion for the instrument voltage limiter for my 69 charger that I saw on Moparts.  Here is the link -  http://www.moparts.org/Tech/Archive/elec/11.html  .   I noticed that when I was doing some other work under the dash, that the metal casing on the voltage limiter was extremely hot to the point I would burn my hand or finger if I touched it. I used one of the laser infrared thermometers and with the car idling for about 5-10 mins, the casing of the voltage limiter got up to temps of 210 ferenheight. To me that is WAY too hot. Is that what they are normally supposed to be at or are they supposed to be a lot cooler? I know the conversion on my parents 70 chally vert that does not have the rallye dash does not get hot like this but it only has the temp and fuel gauge vs. the temp, fuel, and oil pres. gauge that my charger has.

Can anyone shed some light on this before my charger goes up in flames?

Thanks,

Brian

The number of gauges is irrelevant I would bet. The gauges all receive the same maximum amount of voltage (don't they). I am no electrician but I am guessing you have a defective voltage limiter to the gauges, or something is FUBAR with the conversion?. Isn't 220 degrees the boiling point of water? I don't think you will have a fire issue....at first. But I predict wire insulation/circuit board meltdown with your current situation, or I could be totally wrong?

[resq302]

Never tested the temp on mine, but it will burn me if I grab it. Did you solder it to the case? If so, the case acts like the heat sink to remove the heat from the chip so it lasts longer.

Yes, I did solder it to the case and even replaced the voltage limiter today and still had the same results.  I then pulled it out out and tried adding heat sink alluminum fins to the sides and back of the metal case to help disipate the heat too. 

Topher- did you do the home made radio shack conversion or did you purchase one from Charger Specialties?

69dodgecharger - I highly doubt it is the voltage limiter as that is what I thought and for $2, I replaced it with a new one that did the same thing.

[y3chargerrt]

This is what I put in Brian.

http://rt-eng.com/mediawiki/index.php/RTE_limiter

[resq302]

Ok, did a little digging on google to see exactly what transpires with the 12v to 5v reduction with the voltage limiter/regulator that was used in the conversion that was archived in the tech electrical section. According to how a voltage reducer works, in order to drop the voltage from 12 to 5 volts, heat is "generated" to by resistance to drop the voltage. So it is inevitable to have this type of set up with out it heating up. The only way to disipate the heat is by form of a heat sink like the original poster did with that finned looking thingy. Guess if I want it to be cool and prevent any electrical issues, I will have to do away with the stock look and make something that will work for me or spend $50 or so and make it look correct.

[69DodgeCharger]

Good thing I'm not an electrician! Does seem odd to be that hot though.

[Topher]

Yep. I installed it on the inside of my gauge and used the body as a heat sink. 1st Gen gauges are different, which is why I did it that way.

[Ghoste]

I made one and used a fairly large aluminum heat sink when I did.  The instructions I followed at the time advised to do so and that was good enough for me.

[y3chargerrt]

50 bucks will buy you alot of piece of mind Brian. The RTE guys are usually at Carlisle so you can talk to them there.

[elacruze]

12v computer case fans are your best friend. I use them all over the place to cool hot zones.

[W4ATL]

The more instruments that need voltage the hotter the voltage regulator will get. If it is putting out 5V the voltage regulator is fine. You need more heat sink. One of the "winged thingys" will be good. There is also some heat conduction cream that you can put between the regulator/case and the additional heat sink to aid in heat transfer.  210 is way too hot. 150 max is more like it but it may get hotter in the heat of the summer.

More heat sink and you will be OK.

[bakerhillpins]

The more instruments that need voltage the hotter the voltage regulator will get. If it is putting out 5V the voltage regulator is fine. You need more heat sink. One of the "winged thingys" will be good. There is also some heat conduction cream that you can put between the regulator/case and the additional heat sink to aid in heat transfer.  210 is way too hot. 150 max is more like it but it may get hotter in the heat of the summer.

More heat sink and you will be OK.

The "winged thingys" are generally referred to as Heat Sinks in the industry. The "heat conduction cream" is generally referred to as Thermal Paste, Thermal Compound, Heat Sink Compound or in some cases a Thermal Bond/Bridge agent. You can pick the Thermal paste up at any Best Buy in the computer section as those guys use it for upgrading the heat systems when they overclock their CPUs. I just bought some at my local Best Buy to attempt a repair on my Xbox360. The brand they sell is Dynex and runs $10 for a little tube. http://www.bestbuy.com/site/Dynex%26%23174%3B+-+Thermal+Compound/9609458.p?skuId=9609458&id=1218152478854 You don't need much, its only supposed to fill the microscopic spaces between the heat sink and the device.

In general you should orient the fins of the heat sink in the direction of natural heat flow, i.e. Fins should be up/down when installed Vertically. If its a horizontal install then its really a best guess with regard to air flow.

Mounting to the frame can be an effective heat sink but it all boils down to the # of sq inches of physical contact between the heat source and sink. Basic bolts are not effective heat conductors (think about how much actual surface contact you have there). You need to make sure that you have as much surface contact as possible. Filling a void with thermal compound IS NOT a solution to a bad physical interface, its only effective for the tiny (microscopic) voids in the interface, That's why its got the consistency of toothpaste. For the most part it squeezes out. Which is why a little goes a LONG way. Also, dry paste is just as bad or worse as no paste. So if you disassemble a heat sink and don't clean/prep and reapply the paste then you have just made the thermal situation worse.

[resq302]

Well, for giggles I pulled out the conversion and bought another voltage regulator and capacitor with a decent sized heat sink alluminum finned thing like the one on the moparts.com tech archive electrical section.  Did it up the same exact way as that with the wires and all and attached that into the stock spot.  Temps got up to 170-172 F degrees.  Still way too hot for me.  I pulled it all out and am now going with the RTE one.  According to his site, his does not get hot.  We shall soon see.  I just dont want to be driving the 3 hours out to Carlisle and have the car burn up with me in it.

[y3chargerrt]

Smart move Brian. See you in Carlisle...Ron